Method and apparatus for measuring consumption of oxygen



Dec. 11, 1956 c. ANZI ET AL 2,773,497

METHOD AND APPARATUS FOR MEASURING CONSUMPTION OF OXYGEN Filed March 8, 1954 INVENTOR5 COSTANTINO ANZI VITTORlO CAPRARO MZZSM ATTORNEY5 United States Patent METHUD AND APPARATUS FQR MEASURENG CDNSUMPTION 0F OXYGEN Costautino Anzi and Vittorio Capraro, Milan, ltaiy, assigners to Carlo Erba, S. P. A., Milan, Italy, a firm Application March 8, 1954, Serial No. 414,816 Claims priority, application Italy lvinrch 1%, H53 2 Claims. (6i. 128--2.'7)

It is known that the measurement of basal metabolism and the measurement of O2 consumed in an oxidation, chemical or biological process, is, in medical and biological practice, currently performed by means of instruments called metabolimeters, in which a pneumatic bell, charged with a known quantity of 05., is utilized as a reservoir-supplier of O2, and the measurement of the quantity of 02 consumed by the subject under examination is obtained by calculating at 0 of temperature, and at 760 mm. Hg of pressure and dryness, the volume of 02 which the pneumatic bell has supplied to the subject under examination.

The employment of the pneumatic bell necessitates calculation in order to ascertain the quantity of 0:; consumed in gramrnolecules. The purpose of the present invention is not only to obviate such calculations, but to make possible performing measurements of unlimited duration, with an accuracy of measurement considerably greater than that which is normally attainable with the current methods.

The principles of the invention are illustrated in the accompanying drawing which is a diagrammatic representation of apparatus embodying the invention and suitable for practising the method of the invention.

The apparatus comprises an electrolytic cell lll, capable of developing 02, connected by means of a tube to th thermostatic chamber 11 in which the oxidation process takes place (e. g., respiration). The chamber is equipped with a mechanical system for the circulation and purification of air, consisting of the pump 12 and the purifier 13. The entire volume comprising the chamber 11, the pump 12, the purifier 13, the bell 14 placed around the electrode 15 and the connecting tubes, is hermetically sealed to the outside. An electrical instrument 16 (amperesecondimeter, amperemeter, or coulombometer) aifords time measurement and integration of the quantity of electricity supplied by the direct-current generator 17 to the electrolytic cell 10.

The functioning of the system is as follows:

The electrode 15 immersed in the electrolyte releases 02 in quantities directly proportional to the quantity of electricity passing through it (Faradays law), exactly one gram-atom of 02 every 2 96.540 Coulombs (electro-chemical equivalent), independently of temperature and pressure. The electric current passing through the electrolytic cell depends both on the voltage applied to it and on the total electrical resistance of the circuit (Ohms law). Assuming the voltage supplied by the generator 17 to be constant, and the resistances in ohms of the conductors, the instrument, the internal resistance of the generator itself and the resistance of the electrolyte all to be of fixed value, we can regard the strength of the circulating current as depending solely on the resistance of contact between the electrode 15 and the electrolyte,

Patented Dec. 11, 1956 2 or, in the last analysis, depending on the submerged surface of the electrolyte itself.

Should the 02 released by electrode 15 not be consumed in chamber 11, it will tend to produce an overload in the hermetically sealed environment in which it develops. Such overload will cause a lowering in the level of the electrolyte in cell it and, consequently, a reduction in the submerged surface of electrode 15, with a relative reduction in the amount of 02 produced. Should the 02 not be consumed in 11, there would in the long run be such a reduction in the level of the electrolyte as to nullify the submerged surface of electrode 15, and therefore stop the production of O2.

An analogous and opposite eifect of autoregulation will ensue if the consumption of O2 in 11 exceeds the amount of 02 released; the consequent depression leads to an increase in the level of the electrolyte with a relative increase in the production of 02.

It is evident from the above that the rapidity and sensitivity of the autoregulation system can be varied by regulating the inclination of the electrode in respect of the surface of the electrolyte, its shape and nature, the total volume of the environment in which the gas is released and consumed, etc.

It is clear that the autoregulation system described above enables the pressure (and therefore the content of O2) to be maintained constant in the apparatus, for a consumption of 02 equal to or lower than the maximum 02 releasing capacity of electrode 15.

From the above it will appear that it is possible to read on the instrument 16 the quantity of O2 consumed in an oxidation process of unlimited duration, independently of temperature and pressure; it is also possible to calibrate 16 in litres of 02 or in calories.

It is to be borne in mind that since the quantity of 02 released by electrolysis is dependent solely on the product-current time (ampere-seconds), variations in voltage at the generator 17 will not lead to error in measurement.

Moreover, the apparatus as described above has the considerable advantage of not requiring the supply of 02 from other sources. It will be apparent that numerous variations and modifications of the apparatus shown and described by way of example may be applied Without departing from the principles of the invention.

We claim:

1. Apparatus for the determination of oxygen consumed by an oxidation variable process in biological substrates comprising an electrolytic dissociation cell, a collection chamber around the oxygen-producing electrode of said cell immersed in the cell electrolyte to seal said collection chamber, a constant temperature chamber in which said oxidation process occurs, a conduit connecting said collection chamber with said constant tempera ture chamber, and means for measuring the quantity of electricity consumed by said cell.

2. Apparatus as defined in claim 1 in which said electricity measuring means is calibrated in terms of calories.

References Cited in the file of this patent UNITED STATES PATENTS 1,401,035 Boisen Dec. 20, 1921 2,430,895 Tuve et al. Nov. 18, 1947 OTHER REFERENCES Principles of Electroplating and Electroforming, by Blum et al., third edition (1949), page 259. (Copy in Sci. Lib.). 

1. APPARATUS FOR THE DETERMINATION OF OXYGEN CONSUMED BY AN OXIDATION VARIABLE PROCESS IN BIOLOGICAL SUBSTRATES COMPRISING AN ELECTROLYTIC DISSOCIATION CELL, A COLLECTION CHAMBER AROUND THE OXYGEN-PRODUCING ELECTRODE OF SAID CELL IMMERSED IN THE CELL ELECTROLYTE TO SEAL SAID COLLECTION CHAMBER, A CONSTANT TEMPERATURE CHAMBER IN WHICH SAID OXIDATION PROCESS OCCURS, A CONDUIT CONNECTING SAID COLLECTION CHAMBER WITH SAID CONSTANT TEMPERATURE CHAMBER, AND MEANS FOR MEASURING THE QUANTITY OF ELECTRICITY CONSUMED BY SAID CELL. 